Mercury switch



June 1, 1943. Q w, TRAUTMAN 2,320,683

MERCURY SWITCH Filed Jan. 17, 1941 I U l 1 K g! /2 +11% .9 J A? 9' J/ INVENTOR. 25 22 Cfiard'es Zd'fiauimczn.

- BY ywfw Patented June 1, 1943 MERCURY SWITCH Charles W. Trautman, Elkhart, Ind., assignor, by mesne assignments, to Herbert E. Bucklen, Jr.,

Elkhart, Ind.

Application Jilly 17, 1941, Serial No. 402,759

3 Claims.

This invention relates to mercury switches, and more particularly is directed to the manufacture of a relatively small mercury switch which can be produced by mass production methods at low cost.

The particular form of switch disclosed in the present application is utilized particularly in connection with structures, such as glove compartment lights, trunk lights and similar lights where a tilting action makes and breaks the circuit through the switch, thereby controlling the operation of a secondary circuit.

The present application is a continuation in part of my copending application, Serial No. 368,779, filed December 6, 1940.

One of the main features of the present invention is the provision of a switch of this type which is formed by utilizing a metal cup or sleeve over which is pressed an insulating sleeve which carries a metal cap forming the second terminal of the switch. A body of mercury is retained within the cylindrical chamber formed between the cup and the cap, and in one position, bridges between these two members to close the circuit, while in the other position it lies wholly within the cup member to open the circuit.

As an improvement or modification of this type of construction, I provide means whereby the mercury is able to run into a shallow groove formed between the base of the cap member and the end of the sleeve, which groove forms a means for retaining the mercury in position, stabilizing the action of the switch and insuring that the switch will not have faulty operation.

Another feature of this construction resides in the possibility, by using such a retaining well, of obtaining what may be known as repeat performance in the switch, which is the characteristic that causes the switch to open and close the circuit at predetermined angles of inclination so that it will always operate at such angles, thereby giving positive performance under the desired conditions.

Still another object of the present invention is to provide a construction which may be easily assembled, and which may be made from relatively few and inexpensive parts.

Other objects and advantages of the present invention will appear more fully from the following detailed description which, taken in con' junction with the accompanying drawing, will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention. I

In the drawing:

Figure 1 is a vertical sectional view through one form of switch embodying the present invention; 1

Figure 2 is a corresponding view of a switch embodying the retaining well or recess for stabilizing the action of the mercury;

Figure 3 is an exploded view showing the manner in which the switch may be assembled;

Figure 4 is a view similar to Figure 3 showing the switch in assembled position;

Figure 5 is a sectional view of a modifiecl'lorm of switch; and

Figure 6 is a still further modification of thestructure shown in Figure 5.

Referring now in detail to Figure .1, there is provided a metal cup indicated generally at 5, including an extended cylindrical sleeve portion 6, forming a mercury receiving chamber 1 within which is disposed the body of mercury 8. Pressed over the outer surface of the sleeve is an insulating member 9 formed of Bakelite, fiber,' or the like, which is slightly shorter than the sleeve portion 6 of the cup 5, and is adapted to receive the rubber gasket I!) at the end thereof, surrounding the open end of the sleeve 6. Pressed against the gasket I 0 and the end of the sleeve 6 is a ceramic washer l2, which forms a centering support for and spaces the metal cap l3 away from the end of the sleeve 6. The cap it is press fitted over the ring l2, the gasket l9 and the sleeve 9 thereby closing the chamber it The body of mercury 8, when the switch is tilted in a counter-clockwise direction, moves toward the left of the chamber, forming a bridging contact between the face portion of the cap 13 and the inner surface of the sleeve 6. This closes the circuit through the switch. It will be seen that with this construction, relatively few parts are involved and the switch is capable of manufacture at a relatively low cost. In the modified construction shown in Figure 2, the cup iner'nber thereby forming an annular recess or well at this end of the switch chamber. The cap member I3, which is pressed over the end of the insulating sleeve 9', forms the other electrode for the switch. In this construction, when the mercury 8 has moved to the left hand end of the sleeve it drops into the Well, indicated at l4,-as

it makes contact with thee-ab I3; ni this assition there is a stabilizing or restraining action on the mercury tending to prevent it moving in the opposite direction, and as the switch is tilted in the opposite direction, the mercury will remain in the well until such time as the surface tension is less than the head built up in the main body of mercury 8. At this time the body of mercury 8 will snap out of the well, and due to the head, will move quickly away from the well l4 and cap I3, providing a snap action breaking of contact.

When approaching-switch closing position, the

mercury body plunges into the well I4, thereby making full face contact with the cap member and remains in contact even through appreciable vibration or jarring. This is of decided advantage in that it greatly reduces the possibility of arcing or pitting of the contact face of the cap l3 and also tends to maintain the mercury inv ure 4. Over the extending end of the sleeve 24 there is pressed a thin metal contact member 25 which may be formed of sheet steel. This metal preferably is sufliciently ductile so as to be deformed when the cap 26 is applied under pressure. It will be noted that the member 25 has its flange portion flared slightly outwardly so as to be compressed when the cap member is pressed thereover. This forms a tight fit since the flange is deformed during this pressing operation. This holds the cap 26 securely in position. As will be noted in Figure 4, the mercury body 21, originally disposed in the base of the cup member 20, when moved to the left hand side of the envelope has a portion extending into the well 28, thereby forming a stabilizing end, which prevents the mercury from moving away from the contact member 25 until such time as the switch is tilted to its opposite limiting position. This stabilizing acton prevents flashing of the switch due to vibrations or the like, and insures a positive making and breaking of the contact.

The same type of construction with modified elements is shown in Figure 5, in which the cupmember 30 has the short cylindrical sleeve portion 32 provided with an outwardly tapered end 33 beyond which projects the encircling insulating sleeve 34.

In this form of the invention the cap member,

35 is pressed over the projecting portion of the sleeve 34, being thereby spaced an appreciable distanct from the end 33 of the sleeve 32.- In operation in the form of construction the body 7 of mercury 36, when moved toward circuit clos-i' This prevents undue arcing 'and insures.

projecting cylindrical sleeve portion ofreduced switch is tilted in the opposite direction, all of the mercury will run out of this well to prevent the possibility of short-circuiting the switch by a globule of mercury remaining in this well.

Figure 6 shows a modification of the structure shown in Figure 5, in which the cup 30' has the sleeve portion 32' formed with a stepped shoulder 38 and a reduced cylindrically extending portion 39. This forms a double step or double well at the end of the switch, producing the desired stabilizing action, while still being sufficiently shallow so that the mercury will run therefrom when the switch is tilted in a counterclockwise direction.

However, in the forms of the switch disclosed in Figures 2, 4, 5 and 6, it will be apparent that the well functions as a means of preventing the body of mercury from having intermittent contact with the cap members, holding the mercury in a more or less stabilized position regardless of the vibrations of the switch envelope. As a result, the switch will remain closed until such time as the angle of inclination has been changed a sufiicient amount so that the head of mercury is sufiicient to pull the body of mercury out of the well. The inherent surface tension characteristics of the mercury will prevent leaving any globules of mercury in the well, thus preventing any short-circuiting in the switch. It will be apparent that the cup member forming the main body of the switch envelope may be formed from bar stock by a simple turning operation, and that the cap member can be made as a stamping, While the insulating sleeve can be cut from any desired stock. As a result, the elements of the switch are very economical to manufacture and are readily assembled, as shown in Figure 3, either by hand or by machine operation. Thus, a positively operating, low cost, simplified switch construction is provided having inherent characteristics of stability of operation, rendering it valuable for use in installations where there may be vibration or the like which would normally affect the operation of such a switch. a

I am aware that various changes may be made in certain details of the present construction, and I therefore do not intend to be limited ex- .cept as defined by the scope and spirit of the between the end of said first electrode sleeve and internal diameter such that said beveled end and 65.

ring define an annular well between said cap and said electrode sleeve, stabilizing the mercury when in contact between said cap and said first electrode.

2. A mercury switch. comprising a first electrode including a disc-like head portionand a external diameter, an insulating sleeve pressed over said sleeve portion and abutting said j-head portion at one end thereof,'th opposite end of said sleeve projecting axially beyond. the end oi said sleeve portion, a second electrode having an annular flange pressed over the projecting end of said sleeve and partially overlapping the sleeve portion of said first electrode sleeve portion, said insulating sleeve forming, with the radial end face of said sleeve portion and the inner radial face of said second electrode, an annular channel shaped well forming a stabilizing pocket for mercury in switchslosed position.

3. The switch of claim 2 further characterized in that said first electrode sleeve portion has an internally enlarged end portion'forming a shallow step into said well.

C. W. TRAUTMAN. 

